1. Field of the Invention
The present invention relates to an apparatus for measuring a superior-and-inferior-limb blood-pressure index of a living subject (e.g., a ratio of an inferior-limb blood pressure to a superior-limb blood pressure, or a ratio of a superior-limb blood pressure to an inferior-limb blood pressure), and particularly to the art of evaluating the measured superior-and-inferior-limb blood-pressure index.
2. Related Art Statement
Arteriosclerotic cardiovascular disease is one of major death causes of aged women, e.g., not younger than sixty five years, but there is no general method of finding latent arteriosclerosis. However, it is known that since measuring superior-and-inferior-limb blood-pressure index can be used as a simple and repeatable method to find inferior-limb arterial disease and can be used to check quickly and easily the condition of whole cardiovascular system, the index is useful to identify individuals who need special treatments to reduce its death rate or its incidence rate.
Generally, the above superior-and-inferior-limb blood-pressure index (hereinafter, abbreviated to the xe2x80x9cSIL BP indexxe2x80x9d) is obtained or calculated as the ratio of a systolic blood pressure (xe2x80x9cBPxe2x80x9d) of an ankle as the inferior-limb BP to a systolic BP of an upper arm as the superior-limb BP, that is, ankle/arm BP index (abbreviated to xe2x80x9cAPIxe2x80x9d or xe2x80x9cABIxe2x80x9d). If the measured ankle/arm BP index of a living person is smaller than a threshold, e.g., about 0.9, abnormality may be diagnosed on the person. Thus, even a small change of the systolic BP of the inferior or superior limb greatly affects the diagnosis.
The BP of a living person can change in a short time. For example, the BP of a living person at rest can physiologically change by more than 20 mmHg in ten seconds. Therefore, if there is a time difference between a first time when a systolic BP is measured from an inferior limb and a second time when a systolic BP is measured from a superior limb, the BP of the person may change during the time difference. However, a conventional SIL BP index measuring device does not enable an observer to recognize easily a time difference between a first time when a systolic BP is measured from an inferior limb and a second time when a systolic BP is measured from a superior limb.
It is therefore an object of the present invention to provide a superior-and-inferior-limb blood-pressure (xe2x80x9cSIL BPxe2x80x9d) index measuring apparatus which enables an observer to recognize easily a time difference between a first time when a systolic BP is measured from an inferior limb and a second time when a systolic BP is measured from a superior limb.
(1) According to a first feature of the present invention, there is provided an apparatus for measuring a superior-and-inferior-limb blood-pressure index of a living subject, comprising a first blood-pressure measuring device which measures a first blood pressure of an inferior limb of the subject; a second blood-pressure measuring device which measures a second blood pressure of a superior limb of the subject; index determining means for determining the superior-and-inferior-limb blood-pressure index, based on the first blood pressure measured by the first blood-pressure measuring device and the second blood pressure measured by the second blood-pressure measuring device; a time-information storing device which stores first time information representing a first time when the first blood pressure is measured by the first blood-pressure measuring device, and second time information representing a second time when the second blood pressure is measured by the second blood-pressure measuring device; and a time-information displaying device which displays, in a graph having at least a time-information axis representing time information, a first symbol representing the first time information stored in the time-information storing device, and a second symbol representing the second time information stored in the time-information storing device, along the time-information axis, so that an observer can compare the first and second symbols with each other.
According to this feature, the time-information displaying device displays, in the graph having at least the time-information axis representing the time information, the first symbol representing the first time information stored in the time-information storing device, and the second symbol representing the second time information stored in the time-information storing device, along the time-information axis, so that the observer can compare the first and second symbols with each other. Therefore, the observer can easily recognize visually a difference between the first and second times represented by the first and second symbols.
(2) According to a second feature of the present invention that includes the first feature (1), the time-information storing device comprises a memory which temporarily stores the first time information and the second time information.
(3) According to a third feature of the present invention that includes the second feature (2), the memory comprises a random access memory.
(4) According to a fourth feature of the present invention that includes any one of the first to third features (1) to (3), the apparatus further comprises an operable device which is operable by an operator and which outputs a symbol-move signal representing an amount of operation thereof; and symbol moving means for moving, based on the symbol-move signal supplied from the operable device, one of the first and second symbols relative to the other of the first and second symbols, along the time-information axis of the graph. According to this feature, the operator can move, by operating the operable device, one of the first and second symbols relative to the other of the first and second symbols, along the time-information axis of the graph, so that the first and second symbols coincide with each other in the graph. Based on the amount of operation of the operable device to move one of the first and second symbols relative to the other of the first and second symbols till the first and second symbols coincide with each other, the operator can easily recognize a difference between the first and second times represented by the first and second symbols.
(5) According to a fifth feature of the present invention that includes any one of the first to fourth features (1) to (4), the index determining means comprises means for determining, as the superior-and-inferior-limb blood-pressure index, a ratio of the first blood pressure to the second blood pressure, or a ratio of the second blood pressure to the first blood pressure.
(6) According to a sixth feature of the present invention, there is provided an apparatus for measuring a superior-and-inferior-limb blood-pressure index of a living subject, comprising a first blood-pressure measuring device which includes a first inflatable cuff which is adapted to be wound around an inferior limb of the subject, and a first pulse-wave sensor which detects each of a plurality of heartbeat-synchronous pulses of a first pulse wave produced from a first artery pressed by the first cuff, the first blood-pressure measuring device measuring a first blood pressure of the inferior limb of the subject; a second blood-pressure measuring device which includes a second inflatable cuff which is adapted to be wound around a superior limb of the subject, and a second pulse-wave sensor which detects each of a plurality of heartbeat-synchronous pulses of a second pulse wave produced from a second artery pressed by the second cuff, the second blood-pressure measuring device measuring a second blood pressure of the superior limb of the subject; index determining means for determining the superior-and-inferior-limb blood-pressure index, based on the first blood pressure measured by the first blood-pressure measuring device and the second blood pressure measured by the second blood-pressure measuring device; a peak-magnitude and time-information storing device which stores a first magnitude of a peak of each of the heartbeat-synchronous pulses of the first pulse wave detected by the first pulse-wave sensor, and a first time information representing a first time when the each pulse of the first pulse wave is detected by the first pulse-wave sensor, and stores a second magnitude of a peak of each of the heartbeat-synchronous pulses of the second pulse wave detected by the second pulse-wave sensor, and a second time information representing a second time when the each pulse of the second pulse wave is detected by the second pulse-wave sensor; a distribution displaying device which displays, in a first two-dimensional graph having a time-information axis representing time information and a first-peak-magnitude axis representing first peak magnitude, a distribution of the respective first peak magnitudes of the heartbeat-synchronous pulses of the first pulse wave, stored in the peak-magnitude and time-information storing device, along the time-information axis, and additionally displays, in a second two-dimensional graph which has the time-information axis and a second-peak-magnitude axis representing second peak magnitude, a distribution of the respective second peak magnitudes of the heartbeat-synchronous pulses of the second pulse wave, stored in the peak-magnitude and time-information storing device, along the time-information axis; and a time-information displaying device which displays, along the time-information axis of the first two-dimensional graph in which the first distribution is displaced, a first symbol representing the first time information which is stored in the peak-magnitude and time-information storing device and which represents the first time when the first blood pressure is measured by the first blood-pressure measuring device, and additionally displays, along the time-information axis of the second two-dimensional graph in which the second distribution is displaced, a second symbol representing the second time information which is stored in the peak-magnitude and time-information storing device and which represents the second time when the second blood pressure is measured by the second blood-pressure measuring device.
According to this feature, the peak-magnitude and time-information storing device stores a first magnitude of a peak of each of the heartbeat-synchronous pulses of the first pulse wave detected by the first pulse-wave sensor, and a first time information representing a first time when the each pulse of the first pulse wave is detected by the first pulse-wave sensor, and additionally stores a second magnitude of a peak of each of the heartbeat-synchronous pulses of the second pulse wave detected by the second pulse-wave sensor, and a second time information representing a second time when the each pulse of the second pulse wave is detected by the second pulse-wave sensor. The distribution displaying device displays, in a first two-dimensional graph having a time-information axis representing time information and a first-peak-magnitude axis representing first peak magnitude, a distribution of the respective first peak magnitudes of the heartbeat-synchronous pulses of the first pulse wave, stored in the peak-magnitude and time-information storing device, along the time-information axis, and additionally displays, in a second two-dimensional graph which has the time-information axis and a second-peak-magnitude axis representing second peak magnitude, a distribution of the respective second peak magnitudes of the heartbeat-synchronous pulses of the second pulse wave, stored in the peak-magnitude and time-information storing device, along the time-information axis, and the time-information displaying device displays a first symbol representing the first time information, and a second symbol representing the second time information. Therefore, an observer can easily recognize visually a difference between the first and second times represented by the first and second symbols.
(7) According to a seventh feature of the present invention that includes the sixth feature (6), the peak-magnitude and time-information storing device comprises a memory which temporarily stores the respective first peak magnitudes of the heartbeat-synchronous pulses of the first pulse wave, the respective first time information representing the respective first times when the respective heartbeat-synchronous pulses of the first pulse wave are detected by the first pulse-wave sensor, the respective second peak magnitudes of the heartbeat-synchronous pulses of the second pulse wave, and the respective second time information representing the respective second times when the respective heartbeat-synchronous pulses of the second pulse wave are detected by the second pulse-wave sensor.
(8) According to an eighth feature of the present invention that includes the seventh feature (7), the memory comprises a random access memory.
(9) According to a ninth feature of the present invention that includes any one of the sixth to eighth features (6) to (8), the apparatus further comprises an operable device which is operable by an operator and which outputs a symbol-move signal representing an amount of operation thereof; and symbol moving means for moving, based on the symbol-move signal supplied from the operable device, one of the first and second symbols relative to the other of the first and second symbols, along the time-information axis of a corresponding one of the first and second two-dimensional graphs. The present apparatus enjoys the same advantages as those of the apparatus according to the fourth feature (4).
(10) According to a tenth feature of the present invention that includes any one of the sixth to ninth features (6) to (9), the index determining means comprises means for determining, as the superior-and-inferior-limb blood-pressure index, a ratio of the first blood pressure to the second blood pressure, or a ratio of the second blood pressure to the first blood pressure.